U.S. Pat. No. 4,275,118 to Baney et al. discloses a coating composition comprising an acidic dispersion of colloidal titania, colloidal silica and hydroxylated silsesquioxane in an alcohol-water medium which produces a hard, abrasion-resistant coating when cured on a plastic surface such as polycarbonate.
U.S. Pat. Nos. 4,390,373 and 4,442,168 to White et al. disclose a cured transparent, abrasion resistant coating composition comprising an effective abrasion resisting amount of colloidal dispersion containing colloidal antimony oxide and colloidal silica in a weight rate of less than or equal to about 30:70 in a water-alcohol solution of the partial condensate of R (Si(OH).sub.3) wherein R is an organic radical.
U.S. Pat. No. 4,405,679 to Fujioka et al. discloses a coated shaped article of a polycarbonate type resin of improved abrasion resistance comprising a shaped polycarbonate substrate, an undercoat applied and cured on the substrate, and an overcoat applied and cured on the undercoat comprising a hydrolyzate of an epoxy-containing silicon compound, at least one member of the group of hydrolyzates of organic silicon compounds, colloidal silica and organic titania compounds, and a curing catalyst.
U.S. Pat. No. 4,477,499 to Doin et al. discloses ultraviolet radiation resistant silicone resin coatings having improved thermoformability and shortened required aging achieved by the addition of a Lewis acid compound to the coating composition.
U.S. Pat. Nos. 4,500,669 and 4,571,365 to Ashlock et al. disclose transparent, abrasion resistant coating compositions comprising a colloidal dispersion of a water insoluble dispersant in a water-alcohol solution of the partial condensate of silanol wherein the dispersant comprises metals, alloys, salts, oxides and hydroxides thereof.
European Patent Application No. 851102939 published 05.02.86 entitled "Carbon-Containing Monolithic Glasses Prepared by a Sol-Gel Process" by Baney et al. of Dow Corning Corporation discloses a valuable intermediate which comprises a dispersion of a colloidal metal oxide in a water-alcohol solution of the partial condensate of a silanol having the formula RSi(OH).sub.3, wherein the metal oxide is ZrO.sub.2, SnO.sub.2, ZrSiO.sub.4, B.sub.2 O.sub.3 or La.sub.2 O.sub.3.
Optical quality abrasion resistant coated plastic materials generally require a coating that protects the substrate from the damaging effects of ultraviolet (UV) radiation. Protection from ultraviolet radiation is especially important for polycarbonate, since hydrolytic degradation is apparently accelerated by UV exposure. Conventional UV stabilizers do not impart sufficient protective capacity to abrasion resistant coatings, as sufficient amounts of most typical organic UV absorbers cannot be added to abrasion resistant coatings without adversely affecting hardness and adhesion of the coating. Moreover, typical UV absorbers may gradually become deactivated after prolonged exposure, and also may gradually be leached from the composition.
In Physics of Thin Films, Vol. 5, in "Oxide Layers Deposited From Organic Solutions," Schroder notes that titanium, cerium, antimony, and lead oxides deposited from organic solutions exhibit a steep rise of absorption in the near ultraviolet range of the radiation spectrum, and in the Journal of Applied Polymer Science, Vol. 26, in "Inhibition of Photoinitiated Degradation of Polycarbonate by Cerium (III) Overcoating," Klein et al. disclose coating a polycarbonate substrate with cerous chloride (CeCl.sub.3 /poly(vinyl alcohol) complex.